Swivelling couplings are components that enable two or more lines (also called ducts, pipes, hoses or tubes) to be interconnected axially or angularly, and to eliminate torsion constraints that could affect their physical integrity or internal structure. Hydraulic lines, for instance, being for the most part constructed with braded or intertwined metallic wires or synthetic plastic material, are quite sensitive to torsion constraints.
The use of swivelling couplings is extremely widespread. Many equipment manufacturers and users in all types of industries have been and are regularly in contact with this type of product.
Various technological innovations have been brought forth in industrial fields that use couplings. For instance, in the field of hydraulics, modern heavy weight baring machines are high performing, and their operating pressures have been increased significantly in order to improve productivity. Also, with environmental norms becoming ever more stringent, it is desirable for technology pertaining to hydraulic systems to provide for the reduction or elimination of undesirable leaks and soil contamination.
Some significant challenges with swivelling couplings is the production of a coupling that is reliable, inexpensive, non awkward and non cumbersome. In fact, the size and encumbering aspect of couplings must be minimized, because fluid-containing lines are often regrouped in a restrained space and accessibility is a determining factor in the choice of swivelling couplings.
In addition, it is often very important to respect the original design assembly of lines in order to insure interchangeability of the coupling component as well as its feasibility and penetration into the market. This challenge is omnipresent for this type of product.
For hydraulic systems, most of the swivelling couplings currently available have a poor reputation, as their durability and lifetime is nominal (1000 hours approximatively), and their cost varies between $75.00 and $125.00 for the least complicated models. The market currently sees these components as a necessary evil because of their reduced longevity and the limited choices available. Swivelling couplings are offered by a limited number of manufacturers.
Various types of swivelling couplings are currently on the market and known in the art. Most of these couplings use bearings, often steel ball-bearings or needle-bearings, which are frequently combined with retaining rings. The retaining rings are predominantly composed of carbon spring steel, stainless steel or a copper alloy. The bearing assembly resists the operational constraints in play, which include a variety of forces, pressures, etc., and enable relative movement between the different parts of the coupling.
On a regular basis, such as in the forestry industry among others, these bearing-containing couplings are vertically positioned and are therefore required to support the weight of one or more lines (axial constraints) as well as endure lateral impacts and other forces during operation (radial constraints). The needle- and ball-bearings as well as the retaining rings used in the prior art resist and handle these constraints quite poorly. Premature wearing of the bearings—such as structural fragmentation of the balls or needles—greatly reduces the longevity of the coupling. In addition, in load-sensing hydraulic circuits, couplings are subjected to alternating pressures between, for example, 250 psi and 3000 psi on a regular basis. This periodic high pressure creates conditions that are particularly unsuitable for ball-bearing couplings.
Referring to FIG. 1 (prior art), in a standard swivelling coupling 20 with ball-bearings, the male 22 and female 24 components are provided with corresponding spherical grooves in which the ball-bearings 26 are housed to rotatably interconnect the components. A cap-screw 32 imprisons the balls within the groove. Two O-rings 28a, 28b and a back-up ring 30 are also arranged to cut the pressure of the lubricating fluid and ensure the watertightness of the system. The disadvantages of this coupling include, for instance, insufficient support surfaces of the spherical grooves for axial constraints, which may lead to premature wearing and/or marking of the balls; insufficient smooth support surfaces for radial constraints, which often causes premature wearing; insufficient internal lubrication, since the primary watertight joint slows and retards the fluid supply that lubricates the balls and the internal surfaces; and rapidly suffering from external leaks.
Referring to FIG. 2 (prior art), a swivelling coupling 34 with ball- and needle-bearings, includes a male component 36, a female housing 38, a fixing collar 40, usually twenty to twenty-five balls 42 housed in a groove, needle bearings 44, sealing joint(s) 46, and a torque joint 48. The disadvantages of this coupling 34 include, for instance, insufficient support surface of the groove for axial constraints, which often causes premature wearing and marking of the balls; insufficient internal lubrication, as the primary sealing joint slows the supply of hydraulic fluid to lubricate the balls and the internal surfaces, which often causes premature wearing; and rapidly noticeable external leaks.
Furthermore, despite the evolution in the design with the addition of a needle bearing, the technique employed to guide and seal the coupling assembly remains very similar to the ball-bearing type of coupling, and has the inherent problems thereof.
Other types of swivelling couplings are available and offer different assembly methodologies. The techniques are, for the most part, founded on the use of snap rings in order to resist axial forces, weights or pressures. This type of swivelling coupling is not recommended in vertical applications, because snap rings are not preferred or suitable in supporting the weights in play. The disadvantages of this coupling include, for instance, insufficient internal lubrication and structural weakness of the snap rings in vertical applications, which may cause serious disadvantages; frequent and rapid external leaks being perceptible; risk of contamination of the hydraulic system in the event that the snap ring, situated at the end of the male component, does not detach from the assembly and does not become well immersed in the circulation fluid within the line.
It should also be noted that some swivelling couplings without needle- or ball-bearings are found in the prior art.
U.S. Pat. No. 1,436,392 (GANZ) describes a swivel union including a coupling member having an outstanding flange which abuts on the perimeter rim of a main coupling member and is engaged by an overhanging flange of a coupling nut.
U.S. patent application Ser. No. 10/295,634 (SMITH et al.) describes a hydraulic swivelling connector including a swivel spud with tapering steps which receive various snap rings and is inserted into a connector which has corresponding tapering steps.
United Kingdom patent application No. 2,131,511 A (OSCARSSON) describes a swivel connector including male member inserted within a female member to enclose an O-ring seal against a shoulder to provide a liquid seal, and a collar cemented in place and enclosing the male member.
U.S. Pat. No. 3,877,732 (MOHAUPT) describes a high pressure fluid rotary coupling including a diamond-shaped connector by which fluid is able to leak through certain interstices of the coupling.
U.S. Pat. No. 5,005,877 (HAYMAN) describes a hydraulic coupling with a quick connect/disconnect mechanism, which includes a slidable collar engaging a locking body at cooperating angles to enable the lateral unlocking of the locking body.
In addition, U.S. Pat. Nos. 3,402,253, 3,799,440, 4,006,924, 4,101,148, 4,672,998, 5,174,614, 5,577,775, 5,651,567, 5,716,080, 6,406,065 and United States patent application published under Nos. 2002/0163185, 2003/0067161, and 2005/0140138, describe various couplings of the prior art.
Furthermore, many couplings known in the art are often designed to have dry internal components, or slightly lubricated components. Such traits often lead to functional problems or assembly inefficiencies.
In addition, many couplings known in the art present the disadvantage of deteriorating with time so that their performance decreases as the internal parts interact and become used and/or damaged.
As may easily appreciated from the above-mentioned analyses, the swivelling couplings found in the prior art present numerous disadvantageous, especially in heavy industry and the field of hydraulic systems, and there is presently a need for a new swivelling coupling that overcomes at least some of such disadvantages.